RADIO CONTROL SOARING
Mike Garton 2733 NE 95th Ave., Ankeny IA 50021 E-mail: [email protected]
This column is about electric glider winches and glider-winch sources. For the newbies’ benefit, I’ll provide a basic description of a glider winch. Experienced readers may want to skip ahead to the sections on winch-design issues and the list of American glider-winch suppliers.
What a winch is and how it’s used
The glider winch is widely used for contests and “serious” sport flying. In a nutshell, the winch is an electric motor that reels line onto a cylinder (called a drum). The winch assembly is set up on the downwind side of the field. The line runs from the winch drum, along the ground in the upwind direction, through a pulley staked to the ground (called a “turnaround”), and back downwind to the winch location where it is hooked to the glider.
A pilot uses a foot switch to pulse the motor, forcing the line to tow the glider into the wind. The line’s stretchiness smooths the forces transmitted to the glider. Unlike with hi-starts, winch operators can vary the line tension without changing the glider’s elevator position. Small and large gliders can be launched with the same winch; gentle line tension is needed for small/weak/slow gliders, while moderate tensions are used for large gliders. Low-drag, strong gliders can benefit from an increase in tension late in the launch to slingshot off the end of the line (a zoom launch).
Also unlike a hi-start, a pilot can abort a winch launch by getting off the foot switch, thus decreasing and eventually eliminating the line tension. This often saves a glider when something goes seriously wrong. Any control failure caused by the receiver switch being off, a dying receiver battery, or radio interference on a hi-start can cause a nasty crash accelerated by the energy of the rubber tubing. Another advantage of the winch is that it adapts easily to different field sizes without cutting lines.
Is a winch for everyone?
No. Cost and field-setup hassle are major disadvantages. A winch’s parts alone will run you at least a couple hundred dollars, even if you have the tools, knowledge, and skills to build it yourself. Completed systems range from approximately $500 to $1,200 without the 12-volt battery and battery charger.
Setting up a winch and taking it down is no fun. The motor alone weighs close to 20 pounds. Complete full-size winches start at roughly 23 pounds, plus the 12‑volt, lead‑acid car battery. Well-thought-out designs have a handle built into the winch frame roughly above its center of mass. It helps greatly if your flying field allows vehicles to drive on it while setting up winches; this is usually not an option at sod farms. Winch owners often make carts or dollies to drag winches to the downwind location on the field. There is a nice article about a hand truck converted into a winch and retriever cart on the Quiet Flyer web site.
Smaller/lighter options
The Little BIG Winch (LBW) partially alleviates the cost and weight issues. At 16 pounds plus battery, the LBW and the recommended small tractor battery are easier to set up and put away than a full-size winch, and the LBW is also at the low end of the winch price range. It is lighter and smaller because it uses a special permanent-magnet motor on a small frame. It can launch big gliders and even zoom-launch them. The design was intended to be a convenient winch for personal practice use; it is not designed for nonstop, all-day contest use. Walt Dimick—who makes the LBW—also makes an anodized turnaround and other specialty glider products.
Common motors and availability
The Ford Long Shaft Starter Motor has been the standard winch motor in the US for decades because it is easy to mount a drum on the 5.75-inch shaft protruding from the motor. “Hot” winches often use 6-volt Ford Long Shafts (part 3110) run at 12 volts; tamer winches use 12-volt motors (part 3115) run at 12 volts. Reconditioned 3110 motors have been getting scarce. The sport of lure coursing has created a new motor built to the same specification, providing another source for motors.
Why winches are not trivial to build
Winches are difficult to build from scratch. The winch drums are usually machined from aluminum on a metal lathe. Most winch frames are made from square steel welded together. Unless you have access to machine-shop tools, you must purchase the metal parts from a vendor or have them custom machined (more expensive).
Another reason winch building is not for everyone is the winch motor's high current demand. Douglass Boyd, aka the Winch Doctor, says, "Using a clamp-on ammeter, I've seen spikes of 600 amps; average launch is 120–200 amps." This explains the use of welding cables to run from the battery to the winch.
It is nontrivial to reliably switch that much current. Winches use a foot switch connected to a solenoid or two solenoids in series. The solenoid's purpose is to open and close the electrical contacts on the high-current circuit. Most designs use two solenoids to allow safe operation even when one fails; however, two solenoids will only delay a failure unless you regularly test them to learn when one has gone bad. Replacing the solenoids every year or two is another option.
A solenoid failure on a winch usually means that the contacts weld together and the winch sticks on. A method to quickly cut power to the winch in an emergency is required. This emergency disconnect can be as simple as a pull-out connector (as shown on some commercial winches) or a large knife-style switch.
I have seen solenoid failures a couple of times in the last 20 years of flying. If the pilot cannot get the model off the runaway line quickly, the wings generally fail and the fuselage is strained through the turnaround. If a helper is alert and close enough, they may be able to pull the emergency power switch and save the model.
Safety
- Keep hands and loose clothing away from moving parts.
- The moving line will act like a band saw if it slides across a person.
- Have a quick way to cut power to the winch in an emergency.
- Regularly inspect and test solenoids and high-current wiring.
For excellent articles about winch safety, motor differences, and maintaining winch brushes, see the Winch Doctor’s web site.
Winch parts and upgrades
The Winch Doctor makes “Real Balls”—machined aluminum motor endplates that include ball bearings (standard starter motors use bushings), grease fittings for the bearings, cooling fins, and mounting lugs. These are robust pieces of hardware that are said to reduce current draw by about 20% and extend starter-motor life. The Winch Doctor also sells nice winch kits, complete winches, and other glider specialty products.
Tim McCann (Superskeg) is a winch vendor with a very informative web site. He provides freely downloadable winch plans that include instructions, a parts list, parts sources, a wiring diagram, and an assembly drawing. The plans show his frame and drum.
Laser Arts sells winch and retriever plans. The Laser Arts plans set includes substantial CAD work and is comprehensive. Laser Arts also sells retriever plans.
Vince Botkin sells winches, winch kits, and retrievers. Retrievers hold a spool of light line that can bring the end of the winch line back to the winch. Vince sells one large-spool (20 inches) retriever design and has worked on smaller-spool designs. His frames are square steel tubing, welded, ground smooth, and powder coated. Real Balls kits will fit his frames. Vince’s complete winches are among the least expensive full-size options listed below.
Most people buy their winch lines from Memphis Net and Twine. The recommended product is White Braided Nylon Seine Twine. The 170- or 200-pound test is good for a personal winch, and the 250- or 290-pound test is frequently used at contests.
Sources
- Winch Doctor (Real Balls, winches, winch kits, winch parts, maintenance articles)
Douglass Boyd 4130 SW 117th Ave PMB #168 Beaverton OR 97005 [email protected] www.monkeytumble.com/winchdoc/
- Botkin Designs (winches, winch kit, retriever)
31071 Christine Ln. Nuevo CA 92567 (909) 928-0956 http://hometown.aol.com/botkindesigns/
- Walt Dimick (Little BIG Winch, Ultimate Turnaround)
12724 SE 22nd Ave. Milwaukie OR 97222 (503) 659-7883 www.jrfmachineworks.com/lbwinc/
- Tom Copp / Composite Specialties (F3B winch)
2195 Canyon Dr #D Costa Mesa CA 92627 (949) 645-7032 www.f3x.com/f3bstuff/f3bwinch.htm
- Laser Arts (winch, retriever plans)
- Launch truck article (hand truck converted to winch/retriever)
www.quietflyer.com (click on "Online Articles")
- Superskeg.com (winches, winch kits, turnarounds)
Tim McCann Box 2091 Harrison AR 72602 (870) 365-0023 www.superskeg.com
- Injoy Lure Coursing (new 3110-style winch motors)
(802) 425-3691 www.injoy-1.com
- Mike Wade (winch parts)
- Memphis Net and Twine (braided-nylon winch line)
Transcribed from original scans by AI. Minor OCR errors may remain.
